GB2035481A - Speed control systems - Google Patents

Abstract

A plate 16 rotatably mounted on a fixed shaft 1 is axially displaceable under spring biasing 25, and a second plate 13 rotatably mounted on the shaft 1 is axially displaceable by hydraulic pressure in chamber 26 under control of a centrifugal governor 28 which actuates a spool valve 27. Rotation of plate 16 causes plate 13 to be driven in the opposite sense through rollers 19 mounted on carriages 21 which are pivotally mounted at 24 in a flange 23 of the shaft 1. Axial displacement of plate 13 causes the carriers 21 and thereby the rollers 13 to pivot about points 24 to change the relative radii R 1 and R 2 and thereby the transmission ratio. Plates 13, 16 are coupled to their respective housing parts 9 and 4 by rollers 47, 47' engaged in helical tracks 46 and 46' such that the plates 13, 16 are urged axially into driving engagement with the rollers 19 by transmitted torque. A modification dispenses with the governor valve and uses the pressure generated by an output-driven pump to act on the plate 13 which in this case is the driving member. <IMAGE>

Description

SPECIFICATION Speed control systems This invention relates to a speed control system.

More particularly, the invention concerns a speed control system of the kind which com- prises coaxially mounted and opposed driven and driving plates having opposed annular grooves coaxial with the plates, the grooves forming a generally toroidal track; a power transmitting roller mounted and running within the track, said roller being rotatable about an axis which lies substantially in a plain containing the axis of rotation of the plates and engaging within each of the opposed grooves so that on rotation of the driving plate in one direction power is transmitted therefrom, through the roller, to rotate the driven plate in the opposite direction and in which a said plate is axially displaceable relative to a system part which is restrained from axial displacement and biasing means is provided for urging the plates axially towards each other and into driving engagement with the power transmitting roller. A system of this kind is the subject of our U.K. Patent Specifi-cation No. 1,469,776 in which the driven and driving plates are biased axially towards each other and into driving engagement with the power transmitting roller by centrifugally operable means. It is one object of the present invention to provide an improved arrangement by which the, or one of the, plates is urged into driving engagement with the power transmission roller.It is a further object of the present invention to provide an im proved arrangement for biasing the plates axially towards each other and in a manner which displaces the power transmission roller to effect a change in ratio or angular velocity at which the driving plate is driven relatively to the driven plate.

Having in mind the aforementioned first object, according to the present invention there is provided a speed control system of the kind aforementioned in which said system part is coupled to said axially displaceable plate for axial rotation therewith by means of co-operating track follower means and helical track means co-axial with said plates, said track means and track follower means being arranged so that during axial displacement of said plate which is associated therewith, that plate exhibits a screwed motion relative to the system part and said motion is in a sense which causes the plate to be urged into driving engagement with the roller by torque which is imparted to that plate by its driving engagement with the roller.

Generally and preferably the system part which is coupled by the co-operating track follower means and track means to the appropriate plate will be in the form of a rotatable housing part for that plate. Alternatively however the system part can be a shaft on which the plate is mounted to exhibit rotation therewith and axial displacement with respect thereto.

The track means and track follower means may be in the form of helical splines which slidably co-operate between the system part and the appropriate plate. Preferably however and for convenience of manufacture the track means is in the form of a helical groove (which is conveniently located on the plate) while the track follower means is in the form of a roller, peg, or similar member (conveniently located on the system part) which engages within the groove.

Further according to the present invention and having in mind the aforementioned further object, there is provided a speed control system of the kind aforementioned, said two plates being biased axially towards the roller into engagement therewith and the roller being mounted on a carrier which carrier is pivotally mounted about an axis which is substantially normal to said plane containing the axis of rotation of the plates and is offset from the centre of that roller so that, on axial displacement of the plates, the carrier can pivot to displace radially relative to the axis of rotation of the plates the positions of engagement between the roller and the respective grooves to effect a change in ratio of angular velocity at which the driving plate is driven relative to the driven plate and wherein the two plates are biased towards each other and into engagement with the roller by the admission of fluid under pressure into an expansible chamber associated with one of the plates.

Either the driven or driving plate can be displaceable in response to fluid under pressure as aforementioned while the other plate is preferably spring biased to accommodate axial displacement of that plate effected by pivotal movement of the carrier and in sympathy with axial movement of the plate which is displaceable by fluid pressure. The pressure of fluid to which the expansible chamber is subjected can be variable in accordance with the delivery from a variable output pump or similar device so that the plate will be axially displaced in accordance with the increase or decrease of pressure from such device as required. Valve means can be provided to control the admission of fluid pressure to, and the exhausting of fluid pressure from, the expansible chamber, particularly when the source of fluid is at substantially constant pressure.The valve means is preferably responsive to the speed of rotation of either the driven or driving plate so that such valve means will be controlled in accordance with variations in rotational speed of that plate to cause an adjustment in fluid pressure in the expansible chamber which results in the plate associated with that chamber being axially displaced to vary the ratio at which drive is transmitted through the system as required.

Automatic control for the valve means can be provided by a centrifugal governor which is responsive to the speed of rotation of one or other of the plates so that when that speed varies from a predetermined value the centrifugal governor reacts to adjust the valve means in a sense which controls fluid pressure in the expansible chamber and adjust the transmission ratio through the system to maintain the aforementioned rotational speed of the governed plate substantially constant.

Desirably the plates are accommodated in respective rotatable housing parts for rotation therewith, the housing part for the driving plate may be connected for direct drive, for example to the crank shaft of a vehicle engine, or by a V-belt or similar drive while the housing part of the driven plate may be connected as appropriate to provide an output from the system.

Embodiments of speed control systems constructed in accordance with the present invention will now be described by way of example only, with reference to the accompanying illustrative drawings in which: - Figure 1 is a side view partly in section of a first embodiment of the system in which a driven plate is axially displaceable by fluid pressure admitted to an expansible chamber under control of a centrifugally governed valve; Figure 2 is a part section of the system shown in Figure 1 taken on the line X-X of Figure 1 and illustrates a helical track and track follower coupling between the driven plate and a housing part for that plate;; Figure 3 is a side view, partly in section of a second embodiment of the system in which axial displacement of the driving plate is effected by admission of fluid under pressure to an expansible chamber associated with that plate, the fluid being derived from a variable pressure source, and Figure 4 is a part section of the system shown in Figure 3 taken on the line X-X of that Figure and illustrates a helical track and track follower coupling between the driving plate and its housing part which is similar to the arrangement shown in Fig. 2.

Where possible throughout the following description the same parts or members as referred to in each of the Figures have been accorded the same references.

The speed control system shown in Fig. 1 has a non-rotating shaft 1 which is secured by a nut and flange arrangement 2 to some stationary point, for example a vehicle engine or a vehicle chassis 3. A housing part 4 having on its peripheral wall an integral Vpulley 5 is driven by a V-belt (not shown) for example, from the engine crank shaft and is rotatably supported by roller bearings 6-on the shaft 1 and by a ball bearing race 7 on a flange 8 which is integral with the shaft 1. A similar housing part 9 provided with an integral V-pulley 10 is also rotatably mounted on the flange 8 of the shaft 1 by a ball bearing race 11. The housings 4 and 9 are free to rotate relative to each other and are generally concentric with the shaft 1.

Rotatably mounted on the shaft 1 by roller bearings 1 2 is a generally annular plate 1 3. The plate 1 3 is sealed relative to the shaft and housing part 9 and is axially slidable with respect to the shaft and the housing part 9. The housing part 9 is coupled by means shown generally at 14 to the plate 1 3 in a manner which will be described hereinafter but such coupling 14 ensures that the housing part 9 is rotatable with the plate 1 3 while the latter is capable of axial displacement along the shaft 1 and relative to the housing part 9. Located within the housing part 4 and rotatably mounted by roller bearings 1 5 on the shaft 1 is a second plate 1 6 of generally annular form.The plate 16 is axially slidable along the shaft 1 and is coupled to the housing part 4 by means generally shown at 14' and which is similar to the means 14 so that the plate 1 6 will rotate together with the housing part 4 while being capable of axial displacement along the shaft 1 and relative to the housing part 4.

The opposing faces of the plates 1 3 and 1 6 are each provided with an annular groove 1 7 and 1 8 respectively which are of part circular section. The grooves 1 7 and 1 8 are co-axial with their respective plates and are axially opposed to form a generally toroidal track.The faces of these grooves 1 7 and 18, and thus the plates 1 3 and 16, are held apart by a circumferentially disposed array of, for example, three symmetrically arranged, power transmission rollers of which one is shown at 1 9. Each roller 1 9 rotates about an axis contained in a plane which includes the axis of rotation of the plates 1 3 and 1 6 and the rollers 1 9 impart by friction means a torque from the plate 1 6 to the plate 1 3 so that the latter is rotated in the opposite sense of direction to the plate 1 8.

Each roller 1 9 respectively rotates in bearings 20 and 20a which are carried by a carrier 21 which is pivotally mounted by pins indicated at 22 within an aperture 23 of the shaft flange 8. The carrier 21 together with its roller 1 9 is pivotable about the axis 24 of the pins 22 so that the axis of rotation of the roller 1 9 can swing either side of the vertical in Fig. 1. The axis 24 extends substantially perpendicularly relative to the plane which includes the axis of rotation of the roller 1 9 and that of the shaft 1.

The plate 1 6 is biased relative to the housing part 4 (by one or more springs 25) axially relative to the shaft 1 into engagement with the roller 1 9. The side of the plate 1 3 remote from the plate 1 6 forms, together with the housing part 9, a chamber 26 which is intended to be subjected to fluid under pressure to bias the plate 1 3 axially towards the plate 1 6 and into engagement with the roller 1 9 against the biasing effect of spring 25. Hydraulic fluid pressure within the chamber 26 is controlled by valve means 27 which valve means is itself controlled by a centrifugal governor 28 responsive to the speed of rotation of the housing part 9.

The valve means 27 comprises a spool 29 which is axially slidable in a blind bore 30 formed at the end of the shaft 1 in the chamber 26. The spool 29 is biased relative to the housing part 9 by a spring 31 to a condition in which an annular recess 32 of the spool opens communication between a fluid pressure line 33 and a port 34 which latter is in constant communication with the chamber 26. The line 33 communicates with the output from a constant delivery pump 35 which is driven by the vehicle engine and draws fluid from a hydraulic reservoir 36.

Axial displacement of the spool 29 against its spring biasing closes communication between its annular recess 32 and the port 34 and opens communication between the port 34 and a second annular recess 37 of the spool which latter recess communicates by way of a return line 38 with the reservoir 36. Displacement of the spool 29 against its biasing 31 is effected by the centrifugal governor 28 which comprises bell crank levers 39 which are pivotally mounted at 40 on brackets or a flange 41 extending into the chamber 26 from the housing part 9. With the centrifugal governor inoperative, one leg of each lever 39 extends radially relative to the shaft 1 to engage between the end of the shaft 1 within the chamber 26 and a flange 42 provided on the spool 29. In this latter condition the second leg of each lever 39 extends generally axially of the shaft 1 and is weighted at 43.

Operation of the governor 28 is effected, as aforementioned, by rotation of the housing part 9 relative to the shaft 1 and as the speed of such rotation progressively increases the weights 43 will eventually be displaced radially outwardly of the shaft 1 by the centrifugal force to which they are subjected thereby causing the bell crank levers 39 to pivot at 40 and displace the spool 29 by reaction on its flange 42 against the biasing effect of spring 31. To alleviate friction between the nonrotating spool 29 and the rotating legs of the levers 39 which react against the flange 42, an annular bearing plate 44 is interposed between the bell crank levers and the flange 42 and this plate 44 is mounted for rotation about the axis of shaft 1 by needle roller bearings 45 which are interposed between itself and the flange 42.

We will now consider operation of the speed control system shown in Figure 1 com- mencing from the condition in which the system is shown in that Figure. Assuming that the housing part 4 is connected by a Vbelt through the V-pulley 5 so that the housing part 4 is rotatably driven at variable speed (say from the crank shaft of the vehicle engine) and also that the pump 35 is operative, rotation of the housing part 4 is transmitted through the coupling 14' to rotate the plate 1 6 therewith which causes the plate 1 3 to be rotated in a contra direction as previousiy mentioned.With the roller 1 9 in the position shown whereby the radius R2 with respect to the shaft 1 at which the roller engages the groove 1 7 is greater than the radius R 1 with respect to the shaft 1 at which the roller engages the groove 18, the speed transmission ratio between the plates 1 3 and 1 6 will be at a minimum (while the mechanical advantage for the drive which is transmitted will be at a maximum) so that the speed of rotation of the plate 1 3 is less than that of the plate 1 6-this can be advantageous particularly when starting the vehicle engine since the load presented by the speed control system to the vehicle engine is at a minimum.Upon rotation of the plate 1 3 the housing part 9 is rotated therewith through the coupling 14 to provide an output from the V-belt and groove 10 connection which may be used to drive, for example, auxilliary equipment of the vehicle such as a water pump or generator.

If the speed at which the housing part 9 is rotatably driven is insufficient to displace the governor 28 from its condition as shown, fluid under pressure from the pump 35 is directed by way of recess 32 and port 34 into the chamber 26 causing the latter to expand and displace the plate 1 3 rightwardly in the drawing. This has the effect of pivoting the roller 1 9 in an anti-clockwise direction about the pivot axis 24 of the carriage 21 and displacing the plate 1 6 against the biasing spring 25.During such pivotal movement of the roller 1 9 the radius R2 is progressively decreased while the radius R1 is increased which causes an increase in the speed of transmission ratio between the plates 1 6 and 1 3 and thereby a relative increase in the speed of rotation of the plate 1 3. When the speed of rotation of the plate 1 3 attains a predetermined value, for example that at which the aforementioned auxilliary equipment is desired to be driven at substantially constant speed, the governor 28 is arranged to react in the event that the desired constant speed is exceeded to displace the spool 29 against the biasing of spring 31 and thereby close of communication between fluid pressure from the pump 35 and the chamber 26 and if necessary to open communication between the chamber 26 and the reservoir through the return line 38. Upon opening of the chamber 26 to the reservoir the plate 1 3 can be displaced leftwardly in Figure 1 under the biasing effect of spring 25 on plate 1 6 which reacts through roller 1 9 so causing the carriage 21 to pivot about its axis 24 and increase the radius R2 while the radius R1 is correspondingly decreased.In this way it will be apparent that by appropriate selection of the biasing springs 25 and 31 and character istics of the governor 43 the control system can be arranged to provide the output which is derived from the housing part 9 with a substantially constant speed of rotation when the speed of rotation at which the housing part 4 is driven has a value which may be varied within a predetermined range of such values.

The driving connection 14 between the plate 1 3 and the housing part 9 comprises a helical groove 46 which is machined in the peripheral wall of the plate 1 3 and a button or roller 47 which engages within the groove 46 and is mounted by a stud 48 on the housing part 9. The helical groove 46 is orientated with respect to the shaft 1 so that as the plate 1 3 is axially displaced by fluid pressure in the chamber 26 towards the plate 16, the plate 1 3 exhibits a screwed motion or partial rotation about the shaft 1.This latter screwed motion effected by relative movement of the groove 46 over the button 47 is in the same rotational direction as that in which the plate 1 3 is driven by the roller 1 9 so that the torque effected on the plate 1 3 by its frictional engagement with the roller 1 9 imparts relative rotational movement between the housing part 9 and the plate 1 3 to urge the plate 1 3 axially into closer engagement with the roller 1 9. The coupling 14' between the plate 1 6 and housing part 4 serves a similar purpose to the coupling 1 4 but in the case of coupling 14' it is ensured that the orientation of its helical track 46' which engages with the follower 47' on the housing part 4 will impart screwed axial movement to the plate 1 6 in a sense which ensures that the plate 1 6 is urged axially relative to the housing part 4 into contact with the roller 1 9 as a result of the torque to which the plate 1 6 is subjected between the housing part 4 and the roller 1 9.

The speed control system in the embodiment of Figs. 3 and 4 is similar to the embodiment previously described but differs in a main respect in that the centrifugal governor and spool valve have been omitted and the expansible chamber 26 is in constant communication by way of line 49 through the shaft 1 with the output of a variable delivery pump 35awhich draws hydraulic fluid from the reservoir 36. Furthermore, the housing part 9 is intended to be driven by a variable speed rotary input, conveniently by belt drive on the V-groove 10 from a vehicle crank shaft, while the casing part 4 is intended to provide a rotational output to drive, preferably at substantially constant speed, for example auxilliary equipment of the vehicle by way of a belt drive engaging with the V-groove 5.

The output of pump 35a being variable increases with the speed of the pump and it is this output which is used to expand the chamber 26 or to permit the chamber 26 to contract thereby displacing the plate 1 3 against the biasing spring 25 or permitting the plate 1 3 to be displaced under the effect of the biasing spring 25 respectively. Preferably the pump 35a is arranged to be driven at a speed which is proportional to the rotary speed of the output housing part 4 and indeed the pump 35a is conveniently driven through an appropriate linkage indicated at 50 from the casing part 4. In addition to communicating with the chamber 26, the output from the pump 35 communicates by way of a temperature compensated restrictor 51 and a line 52 with the reservoir 36.

With the system shown in Figs. 3 and 4 inoperative there is no output from the pump 35a and consequently the chamber 26 is in a contracted condition by the plate 1 3 being biased to the end position shown in Fig. 3 by the spring 25 through the roller 1 9 and plate 1 6. Upon initial rotation of the housing part 9, the plate 1 3 is rotated through the coupling 14 while the plate 1 6 which is driven through its frictional engagement with the roller 1 9 has a rotational speed greater than that of the plate 1 3 (since in the initial condition R2 is greater than R1).Consequently, the housing part 4 is driven through the coupling 14' at a greater rotational speed than the housing part 9 and drives the pump 35a accordingly. As the rotational input speed to the plate 1 3 increases so will the delivery from the pump 35a until, at a predetermined rotational speed of the housing part 4, fluid pressure in the chamber 26 attains a value whereby the biasing effect therefrom on the plate 1 3 causes the plate 1 3 to be displaced towards the plate 1 6 against the biasing of spring 25. This latter effect results in the roller 1 9 pivoting with its carriage 21 about axis 24 so reducing the radius R2 and correspondingly increasing the radius R1.As the radius R2 decreases and the radius R1 increases in proportion therewith there is a reduction in the ratio at which rotary speed is transmitted from the plate 1 3 through the roller 1 9 to the plate 1 6 and thereby to the housing part 4 which causes a reduction in the output from the pump 35a. In this way, by appropriate selection of the spring 25 and the effective pressurised area of the plate 1 3 in chamber 26 it can be ensured that the plate 1 3 will be displaced axially relative to the shaft 1 to pivot the roller 1 9 in a manner which will maintain the rotational speed of the housing part 4 substantially constant when the housing part 9 is rotatably driven at a speed which can be varied within a predetermined range of rotatable speeds.

It will be seen from Figure 4 that the helical groove and button follower coupling 14 for the embodiment of Fig. 3 is constructed in the same manner and serves the same purpose as in the earlier described embodiment; this is also true of the coupling 14' in Fig. 3.

Claims (22)

1. A speed control system comprising coaxially mounted and opposed driven and driving plates having opposed annular grooves coaxial with the plates, said opposed grooves forming a generally toroidal track; a power transmitting roller mounted and running within the track, said roller being rotatable about an axis which lies substantially in a plain containing the axis of rotation of the plates and engaging within each of the opposed grooves so that on rotation of the driving plate in one direction power is transmitted therefrom, through the roller, to rotate the driven plate in the opposite direction; a said plate being axially displaceable relative to a system part which is restrained from axial displacement and biasing means being provided for urging the plates axially towards each other and into driving engagement with the roller; and wherein said system part is coupled to said axially displaceable plate for axial rotation therewith by means of co-operating track follower means and helical track means co-axial with said plates, said track means and track follower means being arranged so that during axial displacement of said plate which is associated therewith, that plate exhibits a screwed motion relative to the system part and said motion is in a sense which causes the plate to be urged into driving engagement with the roller by torque which is imparted to that plate by its driving engagement with the roller.

2. A system as claimed in claim 1 in which the system part which is coupled by the co-operating track follower means and track means to said plate comprises a rotatable housing part for that plate.

3. A system as claimed in claim 2 in which rotatable drive is applied to or derived from said plate by way of the housing part.

4. A system as claimed in any one of the preceding claims in which the track follower means and track means comprise helical spines slidably co-operating between said system part and said plate.

5. A system as claimed in any one of claims 1 to 3 in which track means comprises a helical groove within which the track follower means engages.

6. A system as claimed in claim 5 in which the track follower means comprises a roller member which is in rolling engagement with said helical groove.

7. A system as claimed in either claim 5 or claim 6 in which the helical groove is located on the plate and the track follower is carried by the system part.

8. A system as claimed in claim 7 when appendant to claim 2 in which the helical groove is formed in a cylindrical peripheral part of the plate and the track follower is carried by the said housing part.

9. A system as claimed in any one of the preceding claims wherein a first of said plates is axially displaceable relative to a first said system part and the second of said plates is axially displaceable relative to a second said system part; said first system part being coupled to said first plate for axial rotation therewith by first said co-operating track follower means and helical track means and said second system part being coupled to said second plate for axial rotation therewith by second said co-operating track follower means and helical track means, said first and second said co-operating track follower means and helical track means being respectively arranged so that during axial displacement of said plates which are respectively associated therewith each plate exhibits a screwed motion relative to the system part with which it is respectively associated and said motion is in a sense which causes the respective plates to be urged into driving engagement with the roller by torque which is imparted to the respective plates by their driving engagement with the roller.

1 0. A system as claimed in claim 9 in which the first and second system parts comprise first and second housing parts respectively for the first and second plates.

11. A system as claimed in any one of the preceding claims in which a said axially displaceable plate is biased into driving engagement with the roller by the admission of fluid under pressure into an expansibie chamber associated with that plate.

1 2. A speed control system comprising co-axially mounted and opposed driven and driving plates having opposed annular grooves co-axial with the plates, said opposed grooves forming a generally toroidal track; a power transmitting roller mounted and running within the track, said roller being rotatable about an axis which lies substantially in a plane containing the axis of rotation of the plates and engaging within each of the opposed grooves so that on rotation of the driving plate in one direction power is transmitted therefrom, through the roller, to rotate the driven plate in the opposite direction; a said plate being axially displaceable relative to a system part which is restrained from axial displacement and biasing means being provided for urging the plates axially towards each other and into driving engagement with the roller; said two plates being biased axially towards the roller into engagement therewith and the roller being mounted on a carrier which carrier is pivotally mounted about an axis which is substantially normal to said plane containing the axis of rotation of the plates and is offset from the centre of that roller so that, on axial displacement of the plates, the carrier can pivot to displace radially relative to the axis of rotation of the plates the positions of engagement between the roller and the respective grooves to effect a change in ratio of angular velocity at which the driving plate is driven relative to the driven plate and wherein the two plates are biased towards each other and into engagement with the roller by the admission of fluid under pressure into an expansible chamber associated with one of the plates.

13. A system as claimed in claim 1 2 in which a first plate is displaceable in response to the admission of fluid under pressure into the expansible chamber associated therewith and the second plate is spring biased to accommodate axial displacement of that second plate effected by pivotal movement of the carrier and in sympathy with axial movement of said first plate.

14. A system as claimed in either claim 12 or claim 1 3 in which valve means is provided to control the admission of fluid pressure to, and the exhausting of fluid from, said expansible chamber.

1 5. A system as claimed in claim 14 in which the valve means is responsive to the speed of rotation of one of said plates so that said valve means is controlled in accordance with variations in rotational speed of the plate to which it is responsive to cause an adjustment in fluid pressure in the expansible chamber and thereby displacement of the plate associated with the chamber and a variation in the ratio at which drive is transmitted through the system.

1 6. A system as claimed in claim 15 in which the valve means is controlled by a centrifugal governor which is responsive to the speed of rotation of the said one of the plates.

1 7. A system as claimed in either claim 1 5 or claim 1 6 in which the valve means reacts automatically in response to a variation in the speed of rotation of said one plate, said reaction causing an adjustment of the valve means in a sense which controls fluid pressure in the expansible chamber and adjusts the transmission ratio through the system to maintain the said rotational speed of the said one of the plates substantially constant.

1 8. A system as claimed in either claim 1 2 or claim 1 3 in which the expansible chamber is in constant communication with a source of fluid pressure which provides a variable pressure output which output is in constant communication with exhaust by way of a restrictor.

1 9. A system as claimed in claim 1 8 in which said source provides an output the pressure of which increases and decreases in proportion to an increase or decrease respectively in the rotational speed of one of said plates.

20. A system as claimed in claim 1 9 in which fluid pressure is derived from a variable speed pump which is responsive to the speed of rotation of the driven plate so that the output of said pump is proportional to that speed of rotation and wherein the pump is coupled to be driven from said driven plate.

21. A speed control system substantially as herein described with reference to Figs. 1 and 2 of the accompanying illustrative drawings.

22. A speed control system substantially as herein described with reference to Figs. 3 and 4 of the accompanying illustrative drawings.